Many signals in communications and other fields may be represented or produced by combining one or more in-phase components with one or more quadrature components. The components may be sinusoidal components. For example, phase modulated signals (“PSK”), quadrature amplitude modulated (“QAM”) signals, and orthogonal frequency division multiplexed (“OFDM”) signals may be represented by in-phase and quadrature components. Information may be added to a carrier by modulating a carrier in QAM, PSK, or OFDM according to the information. Errors in amplitudes, phase offsets, and/or frequency offsets to the I and/or Q components may cause signal degradation and performance degradation.